Heretofore, in the art, numerous grinder pump designs have been implemented for reducing sewage to a fine particulate size which might be easily disposed. Applicant is aware of grinder pumps presented in U.S. Pat. Nos. 3,961,758; 3,589,623; 3,938,744; 3,726,486; 4,108,386; and 3,650,481. These prior art grinder pumps are of general interest in that they teach the desirability of grinding solid or semisolid matter, typically maintained in a fluid, into an effluent of a nearly homogeneous composition. To achieve such grinding, various types of cutter assemblies have been proposed, such cutters typically including a cutter ring having a cutter disk concentrically maintained therewithin. While this prior art is of general interest, all such art and commercially available assemblies known to applicant have certain inherent drawbacks associated therewith.
One drawback of the prior art is the inability of the grinder pumps to accommodate rubber or other elastomeric type substances which might be passed into the sewage system. Since known grinder pumps operate on the principle of grinding rather than cutting, such elastomeric materials have a tendency to wrap themselves about the cutter disk, between the disk and ring, thereby inhibiting the grinding action.
Further problems inherent with the prior art structures include the inability of the cutter assembly to clean or purge itself. In operation, many known cutters allow a ball of material to congregate about the center of the cutter disk at the point at which the disk is connected to the cutter shaft, this congregation of matter resulting from the fact that the cutter blade does not extend inwardly to the center of the disk, but is only present near the outer periphery where the grinding action occurs. Yet further, known grinder pump designs typically include blade configurations and angles which encourage, rather than discourage, the coagulation of matter at the blade or within cutter passages, such coagulation resulting in a significant decrease in operational efficiency.